the federal deadline for filing taxes. that has fueled speculation the bombing could have been the work of anti-government extremists. speaking at the white house, president obama cautioned against a rush to judgment and vowed to bring the perpetrators to justice. >> we still do not know who did this or why. and people should not jump to conclusions before we have all of the facts. but make no mistake, we will get to the bottom of this. we will find out who did this. we will find out why they did this. any responsible individuals, any responsible groups will feel the full weight of justice. >> witnesses of the bombings described gruesome injuries in a sea of blood. the first witness here is carlos arredondo who has appeared a number of times on "democracy now!" he became a prominent anti-war activist after his son was killed in iraq in 2004 driving around the country and his son's fifth of truck. >> the bomb went off right in front of me. my first instinct was to try to help them. i remembered a fellow who lost both lambs